<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8">
<style>
.btn1, .btn2 {
    border: 5px solid green;
    background-color: blue;
}
.btn1 {
    min-height: 50px;
}
.btn2 {
    height: 50px;
}
</style>
</head>
<body>
<input type='submit' class='btn1' value='' />
<input type='submit' class='btn2' value='' />
</body>
</html>
